1. Field of the Invention
The present invention relates to a wound electrochemical cell, a method for the manufacture thereof and the use of such electrochemical cells.
2. Description of the Related Art
Several types of wound electrochemical cells are known in the art and have been described in the literature. In general a wound cell is composed of a laminate of a cathode material, an anode material, and interposed separators which include an electrolyte. The laminate is wound in a coil, connected to current collectors, and incorporated in a battery case to provide mechanical stability and sealing of the cell.
In some electrochemical cells the current collectors are integral parts of the laminate. Such an electrochemical cell is described in WO 86/03889. In this electrochemical cell the coiled laminate comprises an anode structure in the form of a current collector coated with anode material and a cathode structure in the form of a current collector coated with cathode material. In order to provide a uniform resistance throughout the battery, one of the current collectors has a bare border free of electrode material. This bare border extends beyond the other elements of the coil and is arranged so as to cover the outside of the coil and thereby improve the electrical contact between the current collector and the metal case into which the coil is fitted.
U.S. Pat. No. 3,761,314 discloses a similar electrical cell composed of a coiled laminate comprising an anode structure in the form of a current collector or metal carrier coated on both sides with anode material and a cathode structure in the form of a current collector or metal carrier coated on both sides with cathode material.
The anode metal carrier has a bare edge free of anode material, which edge projects outwardly from one end of the assembly, and the cathode metal carrier has a bare edge free of cathode material, which edge projects outwardly from the opposite end of the assembly. The edge of the anode metal carrier, respectively, and the cathode metal carrier is turned down into overlapping fish scale-like flanges and serves to define and form substantially plane elastically deformable area surfaces at opposite ends of the assembly. When this assembly is sealed in a metal casing, an intimate contact between the respective poles of the casing and the opposite ends of the assembly is obtained.
A similar coiled electrochemical cell is disclosed in U.S. Pat. No. 4,963,446. In this cell, protruding exposed edges of a foil carrier or current collector for the cathode are indented inwardly at intervals to facilitate placement of an insulator ring at the top of the cell after the electrodes have been inserted into a cylindrical metal container, and after fluid electrolyte material has been poured into the cell between the intervals of the indentings. The anode is in contact with the metal container wall and bottom, which thereby serves as the anode terminal. An insulating material is provided between the wall and the cover. The inwardly indented edges of the current collector for the cathode result in an effective insulation of these protruding exposed edges from the container wall, and at the same time in good continuity of contact to a pressure contact in the cover, which serves as the cathode terminal.
A marked property of wound cells as described above is that they are very stable and compact. Further, the wound cell concept with thin electrode plates may result in superior discharge/recharge characteristics. However, there is still a need for improving the compactness.
The object of the present invention is to provide a wound electrochemical cell which is more compact than known wound electrochemical cells. In particular the object of the present invention is to provide a lightweight, wound electrochemical cell which is physically stable and which has discharge/recharge characteristics which are at least as good as those of known wound electrochemical cells.
Further, the wound electrochemical cell according to the invention exhibits discharge/recharge characteristics which are at least as good as those of known wound electrochemical cells, is sufficiently physically stable to be handled under normal circumstances of packaging, transportation and use, and may at the same time be very light and small.